Yohei Kojima

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あらまし 本論文では,DS-CDMA 周波数領域等化(FDE)におけるチャネル推定について述べている.パイロ ットチップ系列の周波数スペクトルが一定ではないため,チャネル推定精度が劣化し,平均ビット誤り率(BER) 特性が劣化してしまう.これまで,筆者らは,チャネル推定精度がパイロットチップ系列にほとんど依存しない最 小平均 2 乗誤差(MMSE)規範に基づくチャネル推定を提案してきた.また,最尤推定に基づく 2 ステップチャネ ル推定を提案し,さらにチャネル推定精度を向上できることを示してきた.しかし,2 ステップ最尤チャネル推定 (MLCE)では,トラッキング能力が問題である.本論文では,1 タップ RLS アルゴリズムに基づくチャネル推定 を用いたときの平均 BER(More)
Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can provide a better downlink bit error rate (BER) performance of direct sequence code division multiple access (DS-CDMA) than the conventional rake combining in a frequency-selective fading channel. FDE requires accurate channel estimation. Recently, we proposed a(More)
Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can provide a better bit error rate (BER) performance than rake combining. However, the residual inter-chip interference (ICI) is produced after MMSE-FDE and degrades the BER performance. Recently, we showed that frequency-domain ICI cancellation can bring the BER(More)
Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can provide better downlink bit error rate (BER) performance of direct sequence code division multiple access (DS-CDMA) than the conventional rake combining in a frequencyselective fading channel. FDE requires accurate channel estimation. In this paper, we propose a(More)
Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can increase the downlink bit error rate (BER) performance of DS-CDMA beyond that possible with conventional rake combining in a frequency-selective fading channel. FDE requires accurate channel estimation. Recently, we proposed a pilot-assisted channel estimation(More)
Physical and tangible representations of information have provided users with intuitive interactions in which users can control information through tangible controls using their hands. In these techniques, flexible materials have often been utilized. For example, clay has been used for an intuitive modeling tool which senses the shape of the clay and(More)
We find a wave vector dependence of the band symmetries for MoS(2)(0 0 0 1) in angle-resolved photoemission. The band structures are found to be significantly different for states of even and odd reflection parities, despite the absence of true mirror plane symmetry away from Γ, the Brillouin zone center, along the line to the K point, at the Brillouin zone(More)
A large-strain, torsional deformation apparatus has been developed based on diamond anvil cells at high pressures, up to 135 GPa with a help of hard nano-polycrystalline diamond anvils. These pressure conditions correspond to the base of the Earth's mantle. An X-ray laminography technique is introduced for high-pressure in situ 3D observations of the strain(More)
あらまし 最小平均二乗誤差(MMSE)規範に基づく周波数領域等化(FDE)とチップ間干渉(ICI)キャンセラ を直接拡散符号分割マルチアクセス(DS-CDMA)に適用すれば,理論的下界に近い優れたビット誤り率(BER) 特性を得ることができる.更なる特性改善には,送信ダイバーシチの適用が有効である.各アンテナで異なる循環 遅延を送信データブロックに与えて,それらを同時に送信する循環遅延送信ダイバーシチ(CDTD)では,等価的 なパス数を増やすことができるため,大きな周波数ダイバーシチ効果が得られる.一方,時空間符号化を行う時空 間送信ダイバーシチ(STTD)では,最大比合成によりアンテナダイバーシチ効果が得られるため,CDTD より優れ た特性が得られると言われてきた.本報告では,CDTD(More)